Railway signaling system



Patented July 29, 1924.

LABS O. GRONDAHL, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO THE UNION 1SWITCH & SIGNAL COMPANY, OF SWISSVALE, PENNSYLVANIA, A CORPORATION OFPENNSYLVANIA.

RAILWAY SIGNALING SYSTEM.

Application filed April 16, 1921. Serial No. 461,781.

To all whom 2'2. may concern.

Be it known that I, LARs O. GRONDAHL, a citizen of the United States,residing at Pittsburgh, in the county of Allegheny and State ofPennsylvania, have invente certain new and useful Improvements inRailway Signaling Systems, of which the following is a specification.

My invention relates to railway signalin and is particularly welladapted to signa ing systems of the type wherein roadside signals aregoverned by track circuits which in turn are influenced by the passageof cars or trains along the'track.

I will describe several forms of signaling -apparatus embodying myinvention, and

will then point out the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is a dia rammatic view showing oneform of signa ing apparatus embodying my invention. Fig. 2 is adiagrammatic view showing anoth r form of apparatus embodying myinvention, and. which ma be used when three-indication signals areesired. Fig. 3 is a view showing a modification of the apparatus shownin Fig. 2 and also embodying my invention.

Similar reference characters refer to similar, parts in each of theseveral views.

Referrin first to Fi 1, the reference characters and E, esignate thetrack rails of a railway over which traflic normally moves in thedirection indicated by the ar- 'row, and which rails are divided byinsulated joints 2 to form a track section A'B. Although I have hereinshown only one such section, it is understood that. a complete signalingsystem embodying my invention will usually comprise a series ofsectionssimilar to the one shown in the drawing and each provided withthe apparatus which. I have shown for section A B. The track section A-Bis provided with a track circuit comprising a source of currentconnected across the rails adjacent the exit end of the section and anelectric lamp L connected across the rails adjacent the entrance end ofthe'sectio'n. As here shown, the source of current for this trackcircuit is the secondary winding 5 of a transformer T, the primary ofwhich is connected with a transmission line 3 to which alternatingspecific kind. The parts of the. track circuit are so adjusted that the,lamp -L is lighted when the track section-is unoccupied, but is darkwhen the section is occupied by a car or train.

Located adjacent the entrance end of the section AB is a signal Scomprising, as here shown, two electric lamps R and G, arranged toindicate stop and proceed, respectively, when li hted. These lamps areconnected in mdltiple across the terminals of the secondary 6 of thetransformer T, the primary of which is constantly supplied with signalincurrent from the transmission line 3. A xed resistance 7 is preferablyincluded in the connectionbetween each lamp and one terminal of thesecondary 6. The branch including the stop lamp R is provided withanother fixed resistance 8, and thebranch including the proceed lam G isrovided with a light responsive cell P WlllCll is so located as to beexposed to the light emitted by the track circuit lamp L. The cell P hasthe characteristic that its electrical resistance varies with, changesin the intensity of the light to which it is exposed. A cell having thischaracteristic may i be made, for example, of selenium, stibnite orcopper oxide, or it may be what is known as a photo-electric cell inwhich the active material is an alkali metal. This cell should be solocated as to receive light from the lamp L but not from any othersource. On account of the low current carrying capacity and highresistance of light sensitive cells it may be necessary to place cell Pin circuit with the high voltage primary of a transformer the lowvoltage secondary of which will then supply current to lamp G.

It will be seen from the foregoing that the electrical resistance of thecell P is comparatively high when the lamp L is extinguished, andcomparatively low when this lamp is lighted. The circuits for the signallamps R and G are so adjusted that when the lamp L is extinguished thevoltage across lamp G is below the value required to light this lamp,and the Volta e across lamp R is above the value require to produceluminosity; whereas when lamp L .is illuminated so that the resistanceof cell P is reduced, the voltage across lamp G becomes sufiicient toilluminate this lamp, and

the voltage across lamp R is then decreased to such value that this lampis dark. It follows, therefore, that when the track section AB isoccupied by a car or train, lamp R is illuminated and lamp G is dark, sothat signal S indicates stop; and that when the track section isunoccupied lamp G is illuminated and lamp R is extinguished so that thesignal indicates proceed.

It will be observed that if the track circuit lamp L should burn out orshould become extinguished for any reason other than the occupancy oftrack section AB by a car or train, the resistance of cell P will behigh, so that signal S will indicate stop.

Referring now to Fig. 2, I have shown a plurality of successive tracksections AB,,

B-C, and CD, which sections are electrically separated by insulatedjoints 2. Each section is provided with a. track circuit which is thesame as that shown in Fig. 1, that is, each track circuit includes thesecondary 5 of the transformer T at the exit end of the section and anincandescent lamp at the entrance end of the section designated by thereference character L with a suitable exponent. Located adjacent theentrance end of each section is asignal designated S with a suitableexponent, and each of which signals comprises three electric lamps R, Yand G, adapted to indicate stop, caution and proceed, respectively, whenlighted. Located adjacent each signal are four light responsive cellsdesignated P P P and P these reference characters being provided withsubscripts corresponding to the location of the cells. The four cells ateach signal are exposed to light from the adjacent track circuit lamp Lbut are so protected that they do not receive light from anv othersource.

Referring specifically to signal S", the stop lamp R is controlled by aVVheatstone bridge device H", which is connected across the terminals ofsecondary 6 of the adjacent transformer T by wires 18 and .22. The twoupper arms of this bridge are formed by the cell P and a fixedresistance 9, while the two lower arms are formed by a fixed resistance10 and the cell B The connecting member of the bridge comprises theprimary of a transformer 11, the secondary of which is connected withlamp R of signal S through wires 12, 13, 14 and 15. The bridge H is soadjusted that when the light responsive cells P and P are illuminated bytrack circuit lamp L no voltageis impressed on the primary oftransformer 11, so that lamp R of signal S is dark. In other words whenlamp L is illuminated, the bridge H is balanced, so that no currentrecast? flows in the connecting member. When lamp L is extinguished,however, the balance of the bridge H is upset, so that current flows inthe primary of transformer 11, and the voltage induced in the secondaryof this transformer is then sufficient to illuminate the stop lamp R ofsignal S.

The caution lamp Y of signal S is connected with the secondary oftransformer 11 at signal S the circuit bein through wires 12, 16, 17 and15. Lamp fof signal S is therefore connected in multiple with the stoplamp R at signal S and is illuminated or extinguished according as lampR of signal S is illuminated or extinguished.

The proceed lamp G of signal S is included in a circuit which receivesenergy from the secondary 6 of transformer T this circuit being fromleft-hand terminal of secondary 6, through wires 18 and 19, lightresponsive cell P wire 20, light responsive cell P lamp G, and wires :21and 29. to the right-hand terminal of secondary 6. Cell P is exposed tothe light from track circuit lamp L while cell P is exposed to lightfrom lamp L This circuit is so adjusted that lamp G is illuminated whenboth'of the light responsive cells are exposed to light, but isextinguished when either or both of these cells are dark. As in Fig. 1,the cells P and P may be in the primal circuit of a transformer, thesecondary of which supplies current to lamp G.

The circuits for the lamps of each signal asre similar to those for thelamps of signal As shown in the drawing, track section AB is occupied bya. car or train Vfiso that lamp L is extinguished. Cell P is thereforedark, so that lamp G of signal S is extinguished. Lamp Y of this samesig nal is extinguished, because the \Vheatstone bridge device H isbalanced. Lamp R of signal S is lighted, however, because thelVheatstone bridge device H is unbalanced. It follows, therefore, thatsignal S indicates stop. In signal S", the proceed lamp G isextinguished because cell P does not re ceive-light. The caution lamp Yof signal S is lighted, however, because the bridge device H isunbalanced. The stop lamp It of signal S is extinguished. because thebridge device H is balanced. Signal S therefore. indicates caution. Asfor sig nal S the proceed lamp G is illuminated because the lightresponsive cells in the circuit for this lamp receive light fromthecorresponding track circuit lamps. Lamp Y is extinguished because thebridge device H is balanced, and lamp R is extinguished because thebridge device H is balanced. It follows therefore that signal Sindicates proceed.

Referring now to Fig. 3, the track circuits and the signals are the sameas in Fig. 2, but

circuit lamp for the section next in advance Considering the auxiliarylamp K for signal S the circuit for this lamp is from secondary 23 oftransformer T through wire 24,. light responsive cellP wire 25, lamp Kand wire 26 to secondary 23. The

cell P is exposed to light from the track circuit lamp L and the circuitis so adjusted that when lamp L is extinguished lamp K is likewiseextinguished, and that when lamp L is lighted lamp K is also lighted.Lamp K constitutes, then, in effeet, a repeater at location C for thelamp L at location B. Toget proper current values a transformer may beinterposed between cell P and lamp K Each of the signals is controlled.by a number of light responsive cells designated P P P P, P", and by twoother light responsive cells designated Q and Q Each cell P'is exposedto light from the adjacent track circuit lamp L, while each cell Q isexposed to light from the adjacent repeater lamp K, as indicated by thedotted lines in the drawing. These cells are so enclosed and protectedthat no light rays can reach them other than from the sources justmentioned.

' Cons'dering signal S for example, the stop lamp R is controlled in thesame manner as in Fig. 2; that is, this lamp is connected with thesecondary of a transformer 11, the primary of which constitutes theconnecting member of the Wheatstone bridge device H It follows,therefore, that this lamp is illuminated when section A-B is occupied,but is extinguished at all other times.

Thecircuit for the from the lefthand termlnal of secondary- 6 oftransformer T through wires 18, 28: and 29, lamp G, wire 30, cell P cellQ and wires 31, 32 and 22 to secondary 6. The parts of thiscircuit areso adjusted that lamp G is illuminated when cells P and Q, receive lightfrom lamps L and K respectively, but that it is extinguished when eitheror both of the cells P and Q are dark. A transformer may be placed incircuit between the light sensitive cells. and lamp G.

The caution lamp Y of signal S is conminals of secondary 6 oftransformer T are a light-responsive cell Q and a resistance 27, thesetwo elements being in series, and. as hereinbefore stated the cell Q isexposed to light from the repeater lamp K The lamp Y 1s provided with acircuit which proceed lamp G is passes from secondary 33 of transformerT through wire 34, cell P lamp Y, wire 35, cell Q and wire 36 tosecondary 33. The partsof this .circuit are soadjusted that when cells Pand Q are both exposed to light the potential across cell Q due tosecondary 6 is equal and opposite to the potential across this cell dueto secondary 33, so that no current flows in the circuit and the lamp 'Yis consequently extinguished. When cell P receives no .light, theresistance of the circuit including lamp Y is so high that this lamp isthen extinguishedregardless of ;the condition of cell Q. When cell Qreceives no light, however, and cell P receives light from lamp L, the

potentials across cell Q and cell P are no longer equal and vsufiicientcurrent then flows in the circuit of lamp Y to light this lamp. Anadditional transformer may be interposed between the light sensitivecells and lamp Y.

As shown in the drawing, track section A-B is occupied by a caror trainW, so that track circuitlamp L for this section is extinguished. Cell Pat location B is consequently dark, so that lamp G of signal S isextinguished. Cell P at this same location is dark, so that lamp Y isextinguished. The bridge device H is unbalanced, however, so that lamp Ris lighted, and, consequently, signal S indicates stop.

At signal S", the'repeater lamp K is dark, because track circuit lamp Lis extinguished. Cell Q is dark, so thatlamp G is extinguished. Cell Qis dark, but cell P receives light from lamp L and so the caution lamp Yis lighted. The stop lamp ,R isdark, because the bridge device H isbalanced. It follows, therefore, that signal S indicates caution.

At signal S, cells P and Q are bothilluminated, so that the proceed lampG is lighted. The potentials across cell Q are balanced, so thatlamp Yis extinguished, and the Wheatstone bridge device H is balanced sothat'the'stop lamp R is extinguished. It follows, therefore, that signalS indicates proceed.

Although I have herein shown and described only three forms of apparatusembodying my invention, it is understood that various changes andmodifications may be made therein within the scope of the appendedclaims without departing from the spirit and .scope of my invention.

Having thus jdescribed my. invention,

what I claim is 1. In combination, a track circuit comprising the trackrails of a railway, a source of current and a lamp; a light-res onsivecell'located in the trackway and su jected to rays from said lamp, and arailway signal located in the trackway and controlled bysaid cell.

2. A railway signaling system comprising a track circuit including alamp, a lightresponsive cell located in the trackway and controlled byrays from said lamp, and a signal located in the 'trackway andcontrolled by said light-responsive cell.

3. In combination, a railway track, a lamp, means controlled by trainspassing along the track for lighting and extinguishingsaid lamp, alight-responsive cell-in the trackway subjected to rays from said lamp,antlil a trackway signal controlled by said cel 4. In combination, atrack circuit comprising track rails, a source of current and a lamp; acell located in the trackway and exposed to light from said lamp andadapted to vary in electrical resistance according to the intensity ofthe light which it receives, and a railway signal located in thetrackway and controlled by said cell.

5. In combination, a section of railway track; a track circuit includingthe rails of said section, a source of current and alamp; aliglit-responsive'cell located in the trackway and affected by the lightrays emitted by said lamp, and a signal located in the trackw'ay andcontrolled by said cell.

6. In combination, a track circuitcomprising track rails, a source ofcurrent and a lamp; a cell located in the trackway and exposed to. lightfrom said lamp and adapted to vary in electrical resistance according tothe intensity of the li ht which it receives, a signal circuit includingsaid cell and a source of current, and a trackway signal included insaid signal circuit and responsive to the variation in the resistance ofthe signal circuit caused by lighting and extinguishing said lamp. y

7. In combination, a track circuitrcomprising track rails, a source ofcurrent and a lamp; a cell located in the trackway and exposed to lightfrom said lamp and adapted to vary in electrical resistance according tothe intensity of the light which it receives, a signal circuit includingasource of current and said cell, and a trackway signal governed by saidcircuit and arranged to give a proceed indication when said lamp islighted and a stop indication when the lamp is extinguished.

8. In combination, a railway track, a lamp, means controlled by trainspassing along said track for varying the voltage applied to said lamp, alight-responsive cell located in the trackway and exposed to light raysfrom said lamp, and traffic governing means in the trackway controlledby said cell.

9. In combination, a railway track divided into sections, a trackcircuit for each section including a source of current and alightemitting device, light-responsive cells exposed to the rays from saidlight-emitting devices, signals for the sections each adapted toindicatestop, caution and proceed, and circuits for said signals controlled bysaid cells.

10. In combination, a railway track, a

lamp, means controlled by trains passing along said, track for varyingthe voltage applied to said lamp, and traflic governing means located inthe trackway and controlled by the light rays emitted by said lamp.

11. In combination, a railway track divided into sections, a trackcircuit for each section including a source of current and alight-emitting device, a repeating light-emitting device for eachsection included in circuit-with a source of current and alightresponsive cell exposed to the track circuit device for the sectionnext in advance, a signal for each section adapted to indicate proceed,caution and stop, and means for causing each signal to indicate proceedwhen both light-emitting devices for the section .are lighted, cautionwhen the track circuit device is lighted'and the repeating device isdark, and stop when both devices for the section are dark 12. Incombination, a track circuit including the rails of a railway track andan electric lamp, and railway traliic governing apparatus located in thetrackway and controlled by the light emitted by said lamp.

13. In combination, a track circuit including an electric lamp, and arailway si nal located in the trackway and controlle by said lamp.

14-. In combination, a railway track divided into a plurality ofsections, a track circuit for each section including a lamp,

a repeating lamp for each section controlled by the trackcircuit for thesection next in advance, and traiiic governing means controlled by saidlamps.

15. In combination, a railway track divided into a plurality ofsections, a track circuit for each section including a lamp, a repeatinglamp for each section controlled by the track circuitfor the sectionnext in advance, and signals for said sections controlled by said lamps.

16. In combination, a railway track divided into sections, a main lampfor each section, means res onsive to a train in each section for controling the lighting of the main lamp for such section, a repeating lampfor each section controlled by the main lamp for the section next inadvance, and trailic governing means controlled by said lamps.

17. In combination, a railway track divided into sections, a main lampfor each section, means responsive to a train in eachnew lamp for thesection next .in advance, and signals for the. sections controlled bysaid lamps, I

18. In combination, a railway track, a plurality of main electric lamps,means controlled by trains passing over/said track for varying thevoltage applied to said lamps, auxiliary lamps for repeating thevariations in illumination of sald main lamps, and traflic governingmeans controlled by said lamps.

19.In'combination, a railway track divided into sections, a trackcircuit for each section including a lamp, a repeating lamp for eachsection controlled by the track circuit lamp for an advancesection, asignal for each section, and a controlling circuit for each si nalincluding a light-responsive cell expose to the track circuit lamp forthe associated section and a light-responsive cell exposed to therepeating lamp for the samesection. r

20. In combination, a railway track divided into sections, a trackcircuit for each section including a lam a repeating lamp for eachsection control ed by the track circuit lamp for an advance section, asignal for each se'ction,.and a controlling circuit .for each signalincluding two light-respong'sive cells in series exposed respectively tothe two lamps associated with such section.

21. In combination, a railway track di-- vided into sections, a trackcircuit for each sectlon including a lamp, a repeating lamp for eachsection controlled by the track circuit lamp for an advance sectlomasignal for each section, a controlling circuit for each. sign andalight-responsive cell exposed to the track circuit lamp for theassociated section, and means governed by the repeating lamp for theassociated section and operating when such lamp is lighted to introducean equal and opposite source of current into circuit.

22. In combination, a railway track divided into secti ns, a trackcircuit for each section includi g a lam a repeating lamp for eachsection control ed by the track circuit lamp for an advance section, asignal foreach section, a controlling circuit for each signal includingtwo sources of current,

i and means for governing the supply of current from said two sources bythe two lamps associated with such section.

23. In combination, a railway track divided into sections, a trackcircuit foreach' section including alamp, a repeating lamp for eachsection controlled by the track circuit lamp .for an advance section, asignal for each section, a controlling circuit for each signalincludingtwo opposing sources of current, and means for governing thesupply of current from said two sources by the two lamps associated withsuch section.

al including a source of current of current connected across the secondof.

said-cells.

25. Railway trafiic controlling apparatus comprising a lamp located inthe trackway and controlled-by the passage of cars or trains, aWheatstone bridge controlled by said lamp, and traflic governing meanscontrolled by said Wheatstone bridge.

26. Railway traiiic controllin apparatus comprising alamp located in thetrackway and controlled by the passage of cars or trains, a Wheatstonebridge connected across a source of current, two opposing le s of suchbridge including resistances an the other two opposing legs includinglight-responsive cells exposed to light from said lamp, the bridgemember of said bridge including the primary of a transformer, and asignal controlled by the secondary of said transformer.

27. Railway traflic controlling apparatus comprising a lamp located inthe trackway and controlled .by the passage of cars or trains, aWheatstone bridge having light-responsive cells in o posite legs exposedto said lamp, and tra c governing means controlled by the brid e memberof said bridge.

28. Railway tra c controlling apparatus comprising a Wheatstone bridge,means 10-.

cated in the trackway for controlling the resistance of at least onelegof said bridge in. accordance with the presence and absence oftrains, a transformer the rimary of which constitutes the bridge mem erof said bridge, and traflic governing means controlled y the secondaryof said transformer.

29. In combination, arailway track divided into sections, a trackcircuit for each section including a lamp, a repeating lamp for eachsection controlled by the track circuit lamp for an advance section, asignal for each section and a controllin circuit for each signalincluding a procee circuit for each signal including twolight-responsive cells exposed respectively to the two lamps for theassociated sectlon, a caution circuit for each signal including twosources of current, a light-responsive cell associated with each sourceand exposed to the track circuit lamp and the repeating lamprespectfully for the corresponding section, a Wheatstone bridge for eachsection connected across a source of current and includinglight-responsive cells exposed to the track circuit lamp for theassociated section, and a stop lamp for each section controlled by thebridge member of the associated bridge.

30. In combination, asection of railway track, a light-responsive celllocated in the trackway, a lamp also located in the trackway forilluminating. said cell, a circuit for said lamp controlled by thepresence and absence of trains in said section, and a track- Waysignalcontrolled by said cell.

31. In combination, a section of railway track, a light-responsivecell'locate-d in the trackway, a lamp also located in the trackway forilluminating said cell, a track circuit including the rails ofsaidsection for controlling said lamp, and a trackway signal controlledby said cell.

32. The method of governing railway trafiic which consists incontrolling the lighting of a lamp according to trafiic conditions,supplying light from said lamp to a lightresponsive cell located in thetrackway, and controlling a trackway traific governing device by saidcell.

33. The method of governing railway traflic which consists in supplyinglight to a light-responsive cell located in the trackway from anelectric lamp also .located in the trackway, and controlling the circuitfor said lamp in accordance with trafic conditions.

' 34. The method of governing railway traflic which consists insupplying light to a light-responsive cell located in the trackway froman electric lamp also located in the trackway, and varying the voltageapplied to said lamp according to trafiic conditions.

35. In combination, a section of railway track, a light-responsive celland a source of light, both located in the trackway, means including atrack circuit for said section for controlling the illumination of saidcell by saidsource, and trackway signaling means controlled by saidcell.

36. In combination, a section of railway track, a light-responsive celland a source of light both located in the trackway, means locatedentirely in the trackway and govened by the presence and absence oftrains in said section for controlling the illumination of said cell bysaid source, and signaling means controlled by said cell.

In testimony whereof I afiix my signature.

